1. Field of the Invention
The present invention relates to an image display (a so-called plasma addressed electro-optical display) using plasma to activate an electro-optical material layer so as to display an image.
2. Description of Prior Art
The resolution and contrast of a liquid-crystal type display unit have been improved by, for example, a so-called active matrix addressing method, in which an active device, such as a transistor, is provided for each display pixel and the active devices are operated.
The foregoing method, however, must use a multiplicity of semiconductor devices, such as thin-film transistors, thus causing a problem of unsatisfactory low manufacturing yield to arise when a display having a large area is manufactured. Thus, there arises a problem in that the cost cannot be reduced.
To solve the foregoing problem, a method has been suggested which employs discharge plasma active devices in place of the semiconductor devices, such as MOS transistors and thin-film transistors.
An image display apparatus (hereinafter called a "plasma addressed electro-optical display") has a stacked structure composed of a liquid crystal layer, which is an electro-optical material layer, and a plasma cell, in which plasma discharge takes place. A thin and dielectric-material plate made of glass the like is disposed between the liquid crystal layer or the plasma cell.
The plasma addressed electro-optical display has a structure that the plasma cell is divided into linear plasma chambers by barrier ribs. The plasma chambers are sequentially switched and scanned, and signal voltages are synchronously applied to transparent electrodes opposite to the plasma chambers in such a manner that the liquid crystal layer is interposed. Thus, the liquid crystal layer is operated.
The plasma addressed electro-optical display is generally arranged in such a manner that a backlight is disposed behind the plasma cell. Light beams emitted from the backlight are allowed to pass through the substrate having the plasma cell, the liquid crystal layer and a color filter. Thus, an image is visibly recognized from a position through the substrate having the color filter.
The above-mentioned structure, however, suffers from reduction in the contrast because liquid crystal portions (hereinafter called "low contrast portions"), which have not been satisfactorily oriented into a predetermined direction, are undesirably included in the field of view.